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20021213: apparent navigation error when display nex2gini rad ars in McIDAS (cont.)


McIDAS needs square image (DX=DY) pixels, whereas GEMPAK is happy
with rectangular pixels. The .nts example I provided does generate
DX=DY so that both McIDAS and GEMPAK users can view the data.
If you pick your own garea and kxky, then you should
maintain square pixels if you want to view the output in McIDAS.

Steve Chiswell

>From: Robert Mullenax <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200212131753.gBDHrD406759

>I confirmed that if I set my nex2gini settings back to what Chiz
>has in his example, then all is well.  So I guess this becomes
>a GEMPAK question as to why the other settings produce an error.
>-----Original Message-----
>From: Unidata Support [mailto:address@hidden
>Sent: Thursday, December 12, 2002 7:21 PM
>To: Robert Mullenax
>Cc: address@hidden
>Subject: 20021212: apparent navigation error when display nex2gini
>radars in McIDAS 
>>From: Robert Mullenax <address@hidden>
>>Organization: Universal Weather
>>Keywords: 200212122157.gBCLvr401500 McIDAS NEXRCOMP
>>I am running the nex2gini script every 10 minutes to generate U.S. base
>>composites, and have been using them in GARP/NMAP2.  Everything
>>seems to work fine.  I have occasionally looked at them in McIDAS 
>>and they looked okay as well.  However, I am thinking of making
>>a sort of radar cgi type thing out of them using McIDAS and
>>noted today that the navigation of the composite
>>seems to be off by approximately 45nm.  The data is correctly displayed
>>in GEMPAK, but all the echoes are shifted ~45nm to the north of their
>>actual location in McIDAS.
>I just looked at the RTNEXRAD/N0R N0R product for ID=TWB and the
>NEXRCOMP/1KN0R-NAT product loaded centered on TWB and the
>correspondence look pretty good:
>NEXRAD Level III N0R for TWB:
>NEXRCOMP/1KN0R-NAT loaded with TWB at the center
>The feature whose location I compared was the upper right most 55 dBZ
>echo to the ENE of Tampa.
>I then IMGCOPYied the 00:22 NEXRCOMP/1KN0R-NAT product centered on TBW,
>made a copy of it, and remapped the 00:20 N0R product for TBW onto the copy.
>The results of this operation can be seen in the following two GIFs
>IMGCOPYed NEXRCOMP/1KN0R-NAT with TWB at the center:
>Remapped NEXRAD Level III N0R for TWB:
>The location of the echos looks pretty consistent to me!?  I animated
>the two displays in McIDAS and see what looks to be at most a 1 pixel
>shift between the two displays.  A 1 pixel shift is more-or-less 1 km,
>so my quickie test does not replicate your 45 nm offset (which would
>be 83.340 km).
>How does your base reflectivity composite compare to ours?  You can
>access ours on papagayo:
>DATALOC ADD NEXRCOMP papagayo.unl.edu
>>I have attached two sample images from
>>the same time, each app looking at the same file.  You will see that
>>McIDAS shows precip covering Mobile Bay for example while
>>GEMPAK does not.  GEMPAK is correct.   I create the grid on
>>an RH Linux 7.2 box and have tried the McIDAS display on the same
>>box (McIDAS 2002a) and on a McIDAS 7.704 Sun SPARC with
>>the same result. <<gem.gif>>  <<MCIDAS.GIF>> 
>>Here is the .nts file I use for the nex2gini:
>>GRDAREA 21.8;-122;48.2;-62.5
>>PROJ    lcc/40;-100;40
>>KXKY    4750;3020
>>GFUNC   n0r
>>RADTIM  current
>>RADDUR  15
>>STNFIL  rad.tbl
>>COMPRESS no                                
>I will see if Chiz has any comments about these GEMPAK settings.
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